Electromagnet vibrator reed switches



Sept. 29, 1964 H. REIFEL 3,151,228

ELECTROMAGNET vIBRAToR REED SWITCHES Filed June 22, 1961 2 sheets-sheet 1 zaga 39 as a5 a, a f5 Inventor: Haadzy Rei/lfd,

Sept. 29, 1964 H. REIFEL 3,151,228

ELECTROMAGNET VIBRATOR REED SWITCHES Filed June 22, 1961 2 Sheets-Sheet 2 United States Patent 3 151 228 Emerson/morini" vrnnnron anni) swrrcnns Harry Reifel, Waltham, Mass., assigner to Stevens- Arnold Inc., South Boston, Mass., a corporation of Massachusetts Filed June 22, 1961, Ser. No. 118,327 Claims. (Cl. 20d-99) Another object of thisiinvention is to provide an improved permanent magnet for polarizing the vibratory reed of a chopper. v

Another object of this invention is to reduce the sizes of choppers. i i

This invention will now be described with reference to the annexed drawings of which:

FIG. 1 is a top plan view of a chopper embodying this invention;

FIG. 2 is a side view of FIG. l;

FIG. 3 is an end view of FIG. 1;

FIG. 4 is an enlarged section along the lines 4-4 of FIG. 2;

FIG. 5 is an enlarged section along the lines 5 5 of FIG. 1;

FIG. 6 is a section along the lines 66 of FIG. 5, and

FIG. 7 is a section along the lines 7-7 of FIG. 5.

A brass frame 1li has a hollow cylindrical portion 11 with a shoulder portion 12 extending perpendicular to the portion 11 at its inner end. A plastic spool 1d extends around the cylindrical portion 11, and has thereon an electromagnetic coil 15. Cylindrical, brass base 16 of reed 17 of magnetizable spring metal is secured within the outer end of the cylindrical frame portion 11. The outer end of the reed 17 is secured within a slot in the inner end of the base 16.

Secured to the inner face of the shoulder portion 12 of the frame 1t), are a permanent magnet 15 formed as a segment of a cylinder having a chord surface as its dat top; spaced-apart, rectangular, pole piece guides Ztl and 21 of magnetizable metal on the flat top of the magnet 18, and a brass frame member 22 formed as a segment of a cylinder having a flat bottom on the tops of the guides 2t? and 21. Pole pieces 24 and 25 are threaded in the guides 2li and 21 respectively, and have llat inner ends spaced from opposite sides of the reed 17 adjacent to the free, inner end thereof.

When the chopper is assembled, the pole pieces 24 and 25 are screwed in until 'their fiat inner ends contact the opposite sides of the reed 17, thus lining up and centering the reed. The reed base 16 is then soldered to the frame portion 11, and the pole pieces are then retracted.

A circular block 28 of electric insulation is attached by screws 29 and 3i) to the outer end of the frame member 22, and has a central opening 32. Extending through the block 28 are the threaded outer ends of bars 34 and 35, on which outer ends are threaded nuts 36 and 37 respectively, which secure the bars to the block 28. The bars 34 and 35 have threaded therein contact adjusting screws 3S and 39 respectively, the inner ends of which touch xed contacts 4t! and 111 respectively, of spring metal in the form of straps having outer portions which extend through the opening 32 in the block 2S, and the outer ends of which extend around the threaded portions of the bars 34 and 35 respectively, and are secured thereto and to the block 28 by the nuts 36 and 37 respectively.

Since the reed 17 is grounded to the frame 10, its inice ner, free end has extended therearound a U-shaped strap 45 of insulation, around which extends a U-shaped strap 46 of contact metal which may be a gold alloy. The strap 46 is connected by a very thin, Very flexible strap 47 of Contact metal which may be an integral part of the strap 46, to a terminal screw 49 which is threaded at the inner side of the block 28 into a nut Sti and at the outer side of the block 2S into a nut 52. The inner ends of the contacts llt) and d1 extend on opposite sides of the strap 46 and are normally spaced therefrom, the spacing being adjustable by the screws 38 and 39 respectively.

The coil 15 has lead wires 54 extending in a trough formed in the shoulder 10, 'the frame member 22 and the block 28. The wires 5d are for connecting the coil to a source of chopper frequency which is not shown and the frequency of which may, for example, be 400 cycles per second. A wire 56 connects the contact straps 46 and 47, and the wires 57 and 58 connect the fixed contacts 4t) and d1 respectively, 'to the associated D.C. source and amplilier which are not shown. A grounding wire 59 is connected through the screw Sti to the frame member 22.

In operation, the magnet 18, through the pole piece guides Ztl and 21, and the pole pieces 24 and 25 respectively, magnetizes the reed 17 so that the field changes produced by the A.C. supplied to the coil 15, cause the reed to vibrate at the applied frequency. Vibration of the free end of the reed results in its contact strap 46 alternately striking the fixed contacts dii and 41, thus closing and opening circuits in which they and the strap 46 are connected.

The adjustable pole pieces no't only serve to line up the reed 17 in the assembly of the chopper, and to magnetize the reed, but are adjusted to change the characteristics of the reed. When the reed of a conventional chopper is displaced by the alternating magnetic lield, its stiffness, and its inertia due to its mass, must be overcome. By making the reed resonant at the applied frequency, the force required to vibrate the reed is greatly reduced. This, however, requires costly precision manufacture, and results in a chopper which operates elliciently at but a single frequency. The pole pieces 2li and 25 of this invention are adjusted to cause the magnetic force they apply to the reed, to balance out its stillness, and to cause the reed to be non-resonant over a wide range. The resonan'tfrequency of the reed is selected to be much higher than the operating frequency. In the disclosed embodiment of this invention, designed to operate at 40() c.p.s., the natural resonant frequency of the reed 17 is 750 c.p.s. The pole pieces 24 and 25 are moved towards the reed until it exhibits no resonance at operating frequencies below 750 c.p.s. This condition is indicated by the reed losing its stiffness and floating in any position in which it is placed@ Thus a single chopper can operate eiiiciently over a wide range of frequencies.

What is claimed, is:

1. An electromagnetic switch comprising a frame of non-rnagnetic material, a permanent magnet formed as a segment of a cylinder having a chord surface, attached to said frame, a frame member of non-magnetic material formed as a segment of a cylinder concentric with said cylinder and having a chord surface parallel and spaced from said chord surface and attached to said frame, a pair of aligned, spaced-apart, rectangular pole piece guides of magnetic metal having at sides in contact with said chord surfaces, axially aligned, pole pieces of magnetic metal threaded in said guides with their inner ends extending into the space between said guides, a reed of magnetic spring metal cantilever supported to said frame and having its free end portion vibratile between the said ends of said pole pieces, contact means on the free end of said reed, xed contact means attached to said c y 1:9 frame and extending opposite and normally spaced from said contact means, and a coil around said reed between said pole pieces and the ixed end of said reed, attached to said frame.

2. An electromagnetic switch comprising a frame of nonamagnetic material having a hollow cylindrical outer portion and having a flange formed on its inner end and extending normal to the axis of said outer portion, a permanent magnet formed as a segment of a cylinder attached to said flange, said magnet having a chord surface at one side of said axis, a frame member' of nonmagnetic material formed as a segment of a cylinder concentric with said cylinder and having a chord surface parallel to and spaced from said chord surface and attached to said flange, a pair of aligned, spaced-apart, rectangular pole piece guides of magnetic metal having flat sides in contact with said chord surfaces and attached to said flange, axially aligned pole pieces of magnet metal threaded in said guides with their axis normal to said axis and with their inner ends extending into the space between said guides, a cylindrical reed base in the outer end oi said outer frame portion, a reed of magnetic spring metal cantilever secured to said base and having its longitudinal center on said axis of said cylindrical frame portion, and having opposed tlat sides extending normal to said axis of said pole pieces and vibratile between but normally spaced from said inner ends of saidA pole pieces, contact means on the free end of said reed, fixed contact means attached to said frame and extending opposite and normally spaced from said Contact means, and a coil around said cylindrical frame portion.

3. An electromagnetic switch comprising a frame of non-magnetic material having a hollow, cylindrical outer portion and having a ilange on its inner end extending normal to the axis of said cylindrical portion, a permanent magnet formed as a segment of a cylinder attached to said flange, said magnet having a chord suriace at one side of said axis, a pair of aligned, spaced-apart rectangular pole piece guides of magnetic metal having corresponding ilat sides on said surface and attached to said frame, axially aligned pole pieces of magnetic metal threaded in said guides with their axis normal to said axis and with their inner ends in the space between said guides, a cylindrical reed base in the outer end of said cylindrical portion, a reed of magnetic spring metal cantilever secured to said base and having its longitudinal center on said axis of said cylindrical portion, and having opposed flat sides extending normal to said axis of said pole pieces, and vibratile between but normally spaced from said inner ends of said pole pieces, a frame member of nonmagnetic material formed as a segment of a cylinder having a chord surface on the opposite sides of said guides attached at its inner end to said ilange, a circular end plate of electric insulation attached to the other end of said frame member, contact means on the free end of said reed, fixed contact means attached to said plate and extending opposite but normally spaced from said contact means, and a coil around said cylindrical portion.

4. An electromagnetic switch comprising a frame of non-magnetic material, a substantially U-shaped magnetic member attached to said frame, said member consisting of a permanent magnet formed as a segment of a cylinder having a llat chord surface forming the curved portion of said member, and non-permanent magnet but magnetizable pole piece guides forming the legs of said member and having dat inner ends on said surface, aligned, magnetizable pole pieces extending through said guides with their inner ends extending into the space between said guide, said pole pieces being adjustable for varying the distance between their said inner ends, a reed of magnetizable spring metal cantilever supported to said frame and extending into the space between said inner ends of said pole pieces, said reed having opposed llat end of said reed, xed contact means attached 'to said frame and normally spaced from said Contact means, and

a coil around said reed between said pole pieces and the fixed end of said reed.

5. An electromagnetic switch comprising a brass frame having a hollow cylindrical outer portion and having a circular flange formed on its inner end and extending normal to the axis of said outer portion, a permanent magnet formed as a segment of al cylinder attached to said flange with vits curved portion concentric with said flange, said magnet having a lat chord surface at one side of said axis, a pair of aligned spaced-apart rectangular pole piece guides of magnetizable metal having iiat ends on said chord surface, said axis extending between said guides, said guides extending normal to said surface, and

Vbeing attached to said. flange, a cylindrical brass reed base secured within the outer end of said outer portion, a ree-d of magnetic spring metal cantilever supported at the end to said base, aligned pole pieces of magnetic metal threaded in said guides with their inner ends extending into the space between said guides, said reed having ilat sides facing said inner ends, contact means on the other end of said reed, said guides having aligned at ends opposite said iiat ends, a brass frame member formed as a segment of a cylinder having its curved portion concentric with said flange and having a ilat chord surface on said aligned dat ends of said guides, said frame member being 4attached at one end to said ilange, a circular plate of electric insulation concentric with said curved portion of said frame member and attached to the other end of said frame member, fixed Contact means attached to said plate and extending opposite and normally spaced from said contact means, and a coil around said cylindrical portion of said frame.

References Cited in the tile of this patent UNTED STATES PATENTS 2,894,094 Howell July 7, 1959 2,922,859 Howell Jan. 26, 1960 2,990,461 Laurien lune 27, 196i 3,043,932 Morris July 10, 1962 

1. AN ELECTROMAGNETIC SWITCH COMPRISING A FRAME OF NON-MAGNETIC MATERIAL, A PERMANENT MAGNET FORMED AS A SEGMENT OF A CYLINDER HAVING A CHORD SURFACE, ATTACHED TO SAID FRAME, A FRAME MEMBER OF NON-MAGNETIC MATERIAL FORMED AS A SEGMENT OF A CYLINDER CONCENTRIC WITH SAID CYLINDER AND HAVING A CHORD SURFACE PARALLEL AND SPACED FROM SAID CHORD SURFACE AND ATTACHED TO SAID FRAME, A PAIR OF ALIGNED, SPACED-APART, RECTANGULAR POLE PIECE GUIDES OF MAGNETIC METAL HAVING FLAT SIDES IN CONTACT WITH SAID CHORD SURFACES, AXIALLY ALIGNED, POLE PIECES OF MAGNETIC METAL THREADED IN SAID GUIDES WITH THEIR INNER ENDS EXTENDING INTO THE SPACE BETWEEN SAID GUIDES, A REED OF MAGNETIC SPRING METAL CANTILEVER SUPPORTED TO SAID FRAME AND HAVING ITS FREE END PORTION VIBRATILE BETWEEN THE SAID ENDS OF SAID POLE PIECES, CONTACT MEANS ON THE FREE END OF SAID REED, FIXED CONTACT MEANS ATTACHED TO SAID FRAME AND EXTENDING OPPOSITE AND NORMALLY SPACED FROM SAID CONTACT MEANS, AND A COIL AROUND SAID REED BETWEEN SAID POLE PIECES AND THE FIXED END OF SAID REED, ATTACHED TO SAID FRAME. 